Axial Spin Research Articles

Effect of axial ligand, spin state, and hydrogen bonding on the inner-sphere reorganization energies of functional models of cytochrome P450.

Using a combination of self-assembly and synthesis, bioinspired electrodes having dilute iron porphyrin active sites bound to axial thiolate and imidazole axial ligands are created atop self-assembled monolayers (SAMs). Resonance Raman data indicate that a picket fence architecture results in a high-spin (HS) ground state (GS) in these complexes and a hydrogen-bonding triazole architecture results in a low-spin (LS) ground state. The reorganization energies (λ) of these thiolate- and imidazole-bound iron porphyrin sites for both HS and LS states are experimentally determined. The λ of 5C HS imidazole and thiolate-bound iron porphyrin active sites are 10-16 kJ/mol, which are lower than their 6C LS counterparts. Density functional theory (DFT) calculations reproduce these data and indicate that the presence of significant electronic relaxation from the ligand system lowers the geometric relaxation and results in very low λ in these 5C HS active sites. These calculations indicate that loss of one-half a π bond during redox in a LS thiolate bound active site is responsible for its higher λ relative to a σ-donor ligand-like imidazole. Hydrogen bonding to the axial ligand leads to a significant increase in λ irrespective of the spin state of the iron center. The results suggest that while the hydrogen bonding to the thiolate in the 5C HS thiolate bound active site of cytochrome P450 (cyp450) shifts the potential up, resulting in a negative ΔG, it also increases λ resulting in an overall low barrier for the electron transfer process.

Quality assurance for diffusion tensor imaging using an ACR phantom: Comparative analysis with 6, 15, and 32 directions at 1.5T and 3.0T MRI systems

Although diffusion tensor imaging (DTI) has been widely used for the quantitative analyses of the integrity of white matter in the brain in clinical and research fields, quality assurance (QA) for DTI has not been fully established. Thus, we suggest a QA guideline for DTI using the American College of Radiology (ACR) Magnetic resonance imaging (MRI) head phantom. In this study, the geometric accuracy, slice-position accuracy, image intensity uniformity, percent signalghosting, low-contrast object detectability, image distortion, fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were measured and evaluated in 1.5T and 3.0T MRI scanners equipped with an 8-channel SENSE head coil. The standard axial spin echo (SE) T1-weighted MR images and DTI with 6, 15 and 32 directions were obtained. Concerning geometric accuracy, image twisting in the three directions was observed due to the inhomogeneity of echo planar imaging (EPI). Image intensity uniformity was significantly lower for DTI than for the standard SE T1-weighted MR images. Percent signal ghosting was higher for images from 3.0T MRI than for images from 1.5T MRI. Low-contrast object detectability was visually identified and measured at a low contrasttonoise ratio (CNR) and a low signaltonoise ratio (SNR). Image distortion changed remarkably to the phaseencoding direction. The present study using the ACR MRI phantom suggests a QA method for DTI with high reproducibility and easy accessibility.

Is any landmark reliable in vertebral enumeration? A study of 3.0-Tesla lumbar MRI comparing skeletal, neural, and vascular markers

PurposeThis study aimed to determine the reliability of the iliolumbar ligament (ILL), 12th costa, aortic bifurcation (AB), right renal artery (RRA), and conus medullaris (CM) for numbering of vertebral segments. Subjects and methodsFive hundred five patients underwent routine lumbar MRI examinations including a cervicothoracic sagittal scout and T1 and T2-weighted sagittal and axial turbo spin echo images. Images were evaluated by two radiologists separately. ResultsThe identifiability of ILL and 12th costa were 85.7% and 48.1%. AB, RRA, and CM were located more caudally in lumbarized S1 and more cranially in sacralized L5 cases. ConclusionLandmarks suggested by previous studies are not reliable alternatives to cervicothoracic scout images due to wide ranges of distribution and inconsistencies in identification.

External hip adduction moment and progression of medial tibiofemoral cartilage damage and bone marrow lesions in persons with knee osteoarthritis

Purpose: Gait biomechanics at the hip may affect medial joint loading at the knee in persons with knee osteoarthritis (OA). A greater external hip adduction moment (reflecting torque generation by the hip abductor muscles) during the stance phase of gait may limit excessive hip drop or trunk lean. This, in turn, may prevent excessive medial knee joint loading and eventual progression of knee OA. Little is known about the relationship between the external hip adduction moment and progression of medial tibiofemoral OA as assessed by MRI. We hypothesized that a greater magnitude of the baseline external hip adduction moment is associated with reduced risk of baseline-to-2-year progression of medial tibiofemoral cartilage damage and bone marrow lesions in persons with knee OA. Methods: Participants with knee OA, defined by osteophyte presence in at least one knee, underwent quantitative gait analysis at baseline using an 8-camera Digital Real-Time Eagle motion analysis system and force plate. Inverse dynamics were used to calculate the external hip adduction moment, normalized to %bodyweight*height. Both knees underwent 3.0T MRI at baseline and two year follow-up using double oblique coronal and axial FLASHwe, coronal T1-weighted spin-echo (SE), and sagittal, axial and coronal fat-suppressed turbo spin echo sequences. We assessed cartilage damage and bone marrow lesions using WORMS scoring, blinding readers to hypotheses and all other data. We used logistic regression statistical models with generalized estimating equations (GEE) to account for correlation between the 2 limbs of each person, to assess the association between external hip adduction moment at baseline and baseline-to-2-year cartilage damage progression and bone marrow lesion progression, defined as any worsening of score in the medial compartment as a whole and within each joint surface. Analyses were adjusted for gait speed, age, gender, and disease severity (using K/L radiographic grade). Results are reported as odds ratios (ORs) and 95% confidence intervals (CIs). Results: 204 persons [mean age 64.2 years (±9.9, SD), mean BMI 28.5 kg/m2 (±5.7), 76.5% women] contributing 391 knees comprised the study sample. The mean external hip adduction moment was 4.43 (±0.9, SD) %body weight*height. As shown in Table 1, a greater external hip adduction moment was significantly associated with a reduced likelihood of cartilage damage progression in the medial tibiofemoral compartment and also at the medial femoral surface. After adjustment for the indicated covariables, these associations were no longer statistically significant at the 5% level. Table 2 shows the means (±SD) of the external hip adduction moment at baseline for knees with and without cartilage damage and bone marrow lesion progression in specific subregions. In analyses of specific regions, a greater external hip adduction moment was significantly associated with a reduced likelihood of cartilage damage progression at the posterior femoral subregion [OR per 1 unit of external hip adduction moment (95% CI): 0.51 (0.31, 0.86)] and bone marrow lesion progression at the central femoral subregion [OR per 1 unit (95% CI): 0.56 (0.35, 0.89)]. Conclusions: In persons with knee osteoarthritis, a greater external hip adduction moment was associated with a reduced likelihood of 2-year medial tibiofemoral cartilage damage progression and bone marrow lesion progression, but these findings were no longer statistically significant in adjusted analyses. The consistently protective direction of the findings at compartment, joint surface, and subregional levels warrants further evaluation at longer follow-up.Table 1Unadjusted and adjusted ORs (95% CIs) for medial tibiofemoral OA progression at 2 yearsMedial Tibiofemoral CompartmentMedial Femoral SurfaceMedial Tibial SurfaceCartilage damage progressionBone marrow lesion progressionCartilage damage progressionBone marrow lesion progressionCartilage damage progressionBone marrow lesion progressionNumber of knees (%) with progression61/391 (16%)87/391 (22%)48/391 (12%)53/391 (14%)29/391 (7%)48/391 (12%)Baseline predictorExternal Hip Adduction Moment (%BW*HT)Unadjusted0.70 (0.51, 0.97)0.75 (0.55, 1.01)0.68 (0.50, 0.93)0.72 (0.48, 1.08)0.88 (0.59, 1.32)0.96 (0.67, 1.37)Adjusted*0.82 (0.58, 1.15)0.85 (0.61, 1.17)0.79 (0.56, 1.12)0.80 (0.53, 1.21)1.07 (0.70, 1.64)1.20 (0.83, 1.75)Results are per 1 unit (%BW*HT) of external hip adduction moment (n = 391 knees from 204 persons)*adjusted for gait speed, age, gender, and K/L grade Open table in a new tab Table 2Means (SD) for the external hip adduction moment in medial tibial and femoral subregionsExternal Hip Adduction Moment (%BW*HT), mean (SD)Cartilage damage progression at 2-year follow-upPosterior femurCentral femurPosterior tibiaCentral tibiaAnterior tibiaNumber of knees (%) with progression20/391 (5%)33/391 (8%)7/391 (2%)25/391 (6%)8/391 (2%)Knees without progression, mean (SD)4.45 (0.88)4.44 (0.90)4.43 (0.89)4.43 (0.89)4.43 (0.89)Knees with progression, mean (SD)3.97 (0.85)4.36 (0.67)3.98 (0.57)4.32 (0.79)4.61 (0.87)Bone marrow lesion progression at 2-year follow-upNumber of knees (%) with progression19/391 (5%)38/391 (10%)12/391 (3%)33/391 (8%)21/391 (5%)Knees without progression, mean (SD)4.43 (0.87)4.47 (0.87)4.43 (0.89)4.44 (0.89)4.43 (0.88)Knees with progression, mean (SD)4.38 (1.19)4.05 (0.92)4.38 (0.84)4.34 (0.79)4.52 (0.96) Open table in a new tab Results are per 1 unit (%BW*HT) of external hip adduction moment (n = 391 knees from 204 persons) *adjusted for gait speed, age, gender, and K/L grade

Cisterna chyli in autosomal dominant polycystic kidney disease

After observing prominent cisterna chyli in several patients with autosomal dominant polycystic kidney disease (ADPKD), we investigated the potential association of cistern chyli enlargement with ADPKD. Retrospective, cross-sectional analysis of abdominal and pelvic MRI at 1.5 Tesla (T) in 70 ADPKD patients (male 44.3%, 20-83 years, median = 53 years) were compared with 70 age and gender matched control subjects without ADPKD, cirrhosis, or cholestasis. Cisterna chyli diameter was measured on axial single shot fast spin echo (SSFSE) images at the level of T12-L2 and evaluated by multivariable regression models with covariates including estimated glomerular filtration rate (eGFR), total kidney volume (TKV), renal cyst fraction (cyst volume/kidney volume), and liver volume. Subjects with ADPKD had larger median cisterna chyli diameter compared with those without ADPKD (6.1 mm versus 3.4 mm, P < 0.0001). The prevalence of cisterna chyli enlargement more than the median (3.4 mm), was greater in ADPKD than in controls (99% versus 51%, P < 0.0001). On univariate analysis, cisterna chyli diameter was inversely correlated with eGFR (r = -0.41; P < 0.0001) and directly correlated with TKV (r = 0.57; P < 0.0001), total renal cyst fraction (r = 0.61; P < 0.001), and liver volume (r = 0.17; P = 0.040). Multivariable linear regression modeling found a significant association of cisterna chyli diameter with ADPKD diagnosis (B = 2.14; 95% confidence interval [CI]: 0.05-4.23; P = 0.04). Logistic regression analysis confirmed the association of ADPKD with an enlarged cisterna chyli diameter (odds ratio = 68.4; 95%CI: 8.9-524, P < 0.0001). Enlarged cisterna chyli is highly prevalent in ADPKD patients but not in age and gender-matched controls.

Novel MRI finding for diagnosis of invasive placenta praevia: evaluation of findings for 65 patients using clinical and histopathological correlations

To review established magnetic resonance (MR) criteria and describe a new MR finding for the diagnosis of invasive placenta praevia. A retrospective review of prenatal MRI examinations of 65 patients (median age: 35years) who underwent MR for the screening of invasive placenta praevia. All MRIs were performed on a 1.5-T unit, including axial, coronal and sagittal T2-weighted half-Fourier single-shot turbo spin echo imaging. Fifteen patients were diagnosed with invasive placenta praevia. Two experienced radiologists reviewed the MR images and evaluated a total of six MRI features of the placenta, including our novel finding of the placental protrusion into the internal os (placental protrusion sign). Inter-rater reliability was assessed by using kappa statistics. Features with a kappa statistic >0.40 were evaluated using Fisher's two-sided exact test for comparison of their capabilities for placental invasion assessment. Interobserver reliability was moderate or better for the intraplacental T2 dark band, intraplacental abnormal vascularity, uterine bulging, heterogeneous placenta and placental protrusion sign. Fisher's two-sided exact test results showed all these features were significantly associated with invasive placenta praevia. The novel MRI finding of a placental protrusion sign is a useful addition to the established MRI findings for the diagnosis of invasive placenta praevia. • Prenatal diagnosis for an invasive placenta is essential for perinatal planning. • Magnetic resonance imaging provides useful information for the diagnosis of invasive placenta. • The placental protrusion sign is a useful novel MRI finding for predicting invasive placenta.

Regge-Wheeler equation, linear stability, and greybody factors for dirty black holes

So-called "dirty" black holes are those surrounded by non-zero stress-energy, rather than vacuum. The presence of the non-zero stress-energy modifies key features of the black hole, such as the surface gravity, Regge-Wheeler equation, linear stability, and greybody factors in a rather nontrivial way. Working within the inverse-Cowling approximation, (effectively the test-field limit), we shall present general forms for the Regge-Wheeler equation for linearized spin 0, spin 1, and axial spin 2 perturbations on an arbitrary static spherically symmetric background spacetime. Using very general features of the background spacetime, (in particular the classical energy conditions for the stress-energy surrounding the black hole), we extract several interesting and robust bounds on the behaviour of such systems, including rigorous bounds on the greybody factors for dirty black holes.

Automated prostate segmentation in whole-body MRI scans for epidemiological studies

The whole prostatic volume (PV) is an important indicator for benign prostate hyperplasia. Correlating the PV with other clinical parameters in a population-based prospective cohort study (SHIP-2) requires valid prostate segmentation in a large number of whole-body MRI scans. The axial proton density fast spin echo fat saturated sequence is used for prostate screening in SHIP-2. Our automated segmentation method is based on support vector machines (SVM). We used three-dimensional neighborhood information to build classification vectors from automatically generated features and randomly selected 16 MR examinations for validation. The Hausdorff distance reached a mean value of 5.048 ± 2.413, and a mean value of 5.613 ± 2.897 compared to manual segmentation by observers A and B. The comparison between volume measurement of SVM-based segmentation and manual segmentation of observers A and B depicts a strong correlation resulting in Spearman’s rank correlation coefficients (ρ) of 0.936 and 0.859, respectively. Our automated methodology based on SVM for prostate segmentation can segment the prostate in WBI scans with good segmentation quality and has considerable potential for integration in epidemiological studies.

Cystadenoma in a seminal vesicle is cured by laparoscopic ablation

Cystadenoma in a seminal vesicle is cured by laparoscopic ablation

SU-D-WAB-02: MRI-Based Treatment Planning in Brain Radiation Therapy: Validation of An Atlas-Based Pseudo-CT Generation Method

Purpose: To quantify the dosimetric accuracy of an atlas‐based pseudo‐CT (p‐CT) generation method in MRI‐based treatment planning, and to evaluate the influence of specific MRI sequences on p‐CT quality. Methods: For six brain IMRT patients, a p‐CT was generated from an MR image set previously used for target delineation. A research version of Advantage SIM™ software (GE Healthcare) was used to produce the p‐CT. The software uses body segmentation and bone enhancement on the input MRI, to produce a p‐CT image with a contrast similar to that of a bone atlas generated offline. The IMRT plan including the isocenter was copied on to the p‐CT and the dose was calculated in Pinnacle™. The two dose distributions were compared using (1) gamma analysis, and (2) differences between the average DVH for the target volume, and tissue contour. Results: The p‐CT visually co‐registered well with both the MRI and conventional CT in four cases where Axial T1 Spin Echo or Fast Spoiled Gradient‐Recalled Echo images were used. For these cases, the average Gamma Index 3%/3mm pass rates were 96.85%, 95.58% and 95.40%, in the axial, coronal and sagittal planes. On average, the absolute value difference between the average DVHs was 1.74 (max: 6.97) and 0.95 (max: 16.7) percentage points, for the tissue contour and target volume, respectively. Two of the MR image sequences (Axial T2 Flair and Axial T1 Fat Sat images) resulted in poor quality p‐CTs and were not used for dose comparison. Conclusion: A good agreement was seen between the p‐CT and CT dose distributions in this preliminary study, showing the potential for using MRI for both target delineation and dose calculation for brain treatments, with the clinical integration of an automated p‐CT generation method, and appropriate MRI sequences.

Relationship Between the Levels of Normal Conus Medullaris and Body Mass Index in the Turkish Adult Population

Objectives:To establish the normal range of the conus medullaris (CM) in large Turkish adult population and to correlate this position with body mass index and sex.Methods:T2-weighted midline, sagittal and axial spin echo magnetic resonance imaging studies of 1236 patients were assessed to identify

Axial iron coordination and spin state change in a heme c upon electrostatic protein–SAM interaction

A bacterial di-heme cytochrome c binds electrostatically to a gold electrode surface coated with a negatively charged COOH-terminated SAM adopting a sort of 'perpendicular' orientation. Cyclic voltammetry, Resonance Raman and SERRS spectroscopies indicate that the high-potential C-terminal heme center proximal to the SAM's surface undergoes an adsorption-induced swapping of one axial His ligand with a water molecule, which is probably lost in the reduced form, and a low- to high-spin transition. This coordination change for a bis-His ligated heme center upon an electrostatically-driven molecular recognition is as yet unprecedented, as well as the resulting increase in reduction potential. We discuss it in comparison with the known methionine ligand lability in monoheme cytochromes c occurring upon interaction with charged molecular patches. One possible implication of this finding in biological ET is that mobile redox partners do not behave as rigid and invariant bodies, but in the ET complex are subjected to molecular changes and structural fluctuations that affect in a complex way the thermodynamics and the kinetics of the process.

Cardiovascular MRI in Detection and Measurement of Aortic Atheroma in Stroke/TIA patients.

BackgroundAortic Atheroma (AoA) is an independent risk factor for new and recurrent stroke. AoA ulceration and mobility are associated with an increased risk for brain embolism. Transesophageal echocardiography (TEE) is the gold standard for detection and measurement of AoA in stroke/TIA patients. Cardiovascular MRI (cMRI) could be an alternative, non-invasive imaging modality for stroke/TIA patients. The objective of this study was to assess the accuracy and correlation of AoA detected and measured by cMRI versus TEE in patients with recent stroke/TIA.Methods and resultsTwenty-two stroke/TIA patients undergoing TEE as a part of their stroke workup consented to a protocol-mandated cMRI performed on a 1.5 T magnet. The protocol included an axial non-breathhold EKG-gated dual-echo spin echo MRI of the thoracic aorta (TR/TE1/TE2=900/29/69) and a contrast-enhanced breathhold 3D gradient-echo image of the thorax (flip/TR/TE=12/4.0/1.71). Maximum plaque thickness, ulceration (≥ 2 mm) and mobility of AoA were assessed in the proximal (ascending and proximal arch) and distal (distal arch and descending) segments of thoracic aorta by a cardiologist to interpret the TEE and a radiologist to interpret the cMRI. There was good correlation between cMRI and TEE in measurement of plaque thickness in the proximal segments (R=0.73, p<0.0001) and the distal segments (R=0.81, p<0.0001) of the aortic arch (AA). cMRI had a high degree of accuracy in detecting measurable AoA (≥ 1 mm) in the proximal segments (sensitivity 90%, specificity 100%), as well as the distal segments (sensitivity 67%, specificity 100%). cMRI also had a high degree of accuracy in detecting significant AoA (≥ 4 mm) in proximal segments (sensitivity 71%, specificity 93%), as well as distal segments (sensitivity 71%, specificity 100%).ConclusionThe study showed a high degree of accuracy and correlation of AoA detected and measured by cMRI as compared to TEE in patients with recent stroke/TIA. This technique has limitations in detection of AoA ulceration, and protocols assessing AoA mobility need to be developed.

MRI Determination of Knee Effusion Volume: A Cadaveric Study

ABSTRACT Background There is currently limited literature on quantitative determination of knee effusion volume using magnetic resonance imaging (MRI). Purpose To describe a method of knee effusion volume determination using MRI generated models and to demonstrate accuracy of this technique. Materials and methods Using axial T2-weighted turbo spin echo and sagittal SPACE sequences, MRIs of three cadaver knees with multiple saline loads were obtained. Effusions models were created and effusion volumes were estimated using the Rhinoceros software. Estimated and known effusion volumes were compared using a bivariate correlation analysis. Results The SPACE sequence and T2WTSE estimates were highly correlated with the known volumes (R = 0.996 and 0.993 respectively, p &lt; 0.001). Conclusion MRI-generated models of knee effusions provide accurate estimates of knee effusion volumes. Clinical relevance MRI determination of knee effusion volume may provide a useful clinical outcomes tool. Wittstein J, Spritzer C, Garrett WE. MRI Determination of Knee Effusion Volume: A Cadaveric Study. The Duke Orthop J 2013;3(1):67-70.

Assessment of whole body MRI and sestamibi technetium-99m bone marrow scan in prediction of multiple myeloma disease progression and outcome: a prospective comparative study

ObjectivesThis study aims primarily to determine whether whole body MRI (WB-MRI) and Sestamibi Technetium-99m-bone marrow (MIBI) scans in the same patients produce the same estimate of disease load and location,...

Validation of Dual Energy X-Ray Absorptiometry Measures of Abdominal Fat by Comparison with Magnetic Resonance Imaging in an Indian Population

ObjectiveAbdominal adiposity is an important risk factor for diabetes and cardiovascular disease in Indians. Dual energy X-ray absorptiometry (DXA) can be used to determine abdominal fat depots, being more accessible and less costly than gold standard measures such as magnetic resonance imaging (MRI). DXA has not been fully validated for use in South Asians. Here, we determined the accuracy of DXA for measurement of abdominal fat in an Indian population by comparison with MRI.Design146 males and females (age range 18–74, BMI range 15–46 kg/m2) from Hyderabad, India underwent whole body DXA scans on a Hologic Discovery A scanner, from which fat mass in two abdominal regions was calculated, from the L1 to L4 vertebrae (L1L4) and from the L2 to L4 vertebrae (L2L4). Abdominal MRI scans (axial T1-weighted spin echo images) were taken, from which adipose tissue volumes were calculated for the same regions.ResultsIntra-class correlation coefficients between DXA and MRI measures of abdominal fat were high (0.98 for both regions). Although at the level of the individual, differences between DXA and MRI could be large (95% of DXA measures were between 0.8 and 1.4 times MRI measures), at the sample level, DXA only slightly overestimated MRI measures of abdominal fat mass (mean difference in L1L4 region: 2% (95% CI:0%, 5%), mean difference in L2L4 region:4% (95% CI: 1%, 7%)). There was evidence of a proportional bias in the association between DXA and MRI (correlation between difference and mean −0.3), with overestimation by DXA greater in individuals with less abdominal fat (mean bias in leaner half of sample was 6% for L1L4 (95%CI: 2, 11%) and 7% for L2L4 (95% CI:3,12%).ConclusionsDXA measures of abdominal fat are suitable for use in Indian populations and provide a good indication of abdominal adiposity at the population level.

Magnetic resonance imaging of ankle tendon pathology: benefits of additional axial short-tau inversion recovery imaging to reduce magic angle effects

Our goals were to quantify the reduction of the magic angle effect using short-tau inversion recovery (STIR) imaging and to determine the value of adding an axial STIR sequence to the magnetic resonance imaging ankle protocol. Axial STIR sequences were used to measure normal tendon T1 and to estimate signal loss due to the inversion recovery preparation of our clinical protocol. In addition, 102 ankles were imaged with axial fat-suppressed intermediate-weighted fast spin echo and STIR sequences. Two radiologists analyzed the tendons for signal intensity, size, abnormalities, and magic angle effect. The diagnostic value and image quality of the two sequences were compared. We calculated a 50% reduction of signal intensity in healthy tendons on the STIR sequence at TI = 170 ms compared with TI = 0 ms, explaining the decrease in the magic angle effect. Using the STIR sequence, our study demonstrated significantly lower signal intensity within the tendons, more precise tendon size, and a lower magic angle effect compared with the standard intermediate-weighted FSE sequence (p < 0.001). Diagnostic classification of tendon abnormalities using the STIR sequences showed higher sensitivity (82.35% vs. 75.27%) and better agreement with a reference standard than the intermediate-weighted sequences, and superior image quality (p < 0.01). Axial STIR sequences reduce magic angle effects and improve visualization of ankle tendon pathology.

Comparison of MRI and 18F-FDG PET for Evaluation of the Response to Treatment of Patients Diagnosed with Multiple Myeloma: A Prospective Clinical Study

AbstractAbstract 4004 IntroductionAlthough conventional radiography is still the standard staging procedure for newly diagnosed and relapsed multiple myeloma (MM) patients in clinical practice, magnetic resonance imaging (MRI) using T2- and T1-weighted contrasted enhanced images has proved to have advantages over a conventional skeletal survey. Fluoro-desoxy-glucose positron emission tomography (18F-FDG PET) is not yet validated as an imaging method for MM evaluation. The purpose of this study was to prospectively compare MRI and 18F-FDG PET for short-term evaluation of the response in newly diagnosed MM patients and to correlate the imaging assessment with the biological response. Materials and methodsA group of 15 newly diagnosed myeloma patients were treated in a single center. After induction with bortezomib-lenalidomide-dexamethasone (VRD), they all received high dose cyclophosphamide and G-SCF prior to peripheral stem cell collection. The patients were then randomized to either autologous stem cell transplantation (ASCT) with 2 consolidation VRD cycles or 5 VRD cycles. All patients subsequently received maintenance treatment with low dose lenalidomide for 1 year. Imaging was performed at diagnosis, after the first three VRD cycles and immediately before initiating maintenance treatment. The spinal and pelvic MRI protocol consisted of sagittal T1-weighted (T1-w) spin echo and fat-suppressed T2-weighted (T2-w) STIR sequences of the spine, axial and coronal T1-w spin echo and fat-suppressed T2-w STIR sequences of the pelvis and upper parts of the lower limbs and finally a fat-suppressed T1-w sequence after intravenous gadolinium covering the spine, pelvis and upper parts of the lower limbs. The biological response was evaluated according to IMWG criteria. The presence or absence of diffuse bone marrow infiltration (DI), diffuse patchy bone marrow infiltration (DPI) and focal bone marrow lesions (FL) was recorded prospectively. A hypointense T1, hyperintense STIR and enhanced fat-suppressed T1 lesion were scored as FL on MRI scans. The presence of extra-medullary disease (EMD) and the SUVmax of FDG-avid focal lesions were assessed. Complete response (CR) and partial response (PR) were determined by MRI and 18F-FDG PET after induction and before maintenance. CR was defined as the absence of diffuse infiltration or focal lesions for MRI and as the absence of diffuse and/or focal uptake for 18F-FDG PET. The response was considered to be partial if the image differed from CR. We compared the results of the two techniques with the biological response for every patient. ResultsThe 15 patients (5 females, 10 males; age: 55 ± 6 years (mean, SD)) were classified according to the ISS (1, n=6; 2, n=8; 3, n=1) and DSS (IIIA, n=14; IIIB, n=1). At baseline, MRI showed DI, DPI and FL in 3, 7 and 189 cases respectively; the 18F-FDG PET uptake displayed a diffuse homogeneous pattern in 4 patients and a diffuse heterogeneous pattern in 11 patients with only 55 focal uptakes. Five cases of extra-medullary uptake were observed on baseline 18F-FDG PET scans and remained at the follow-up. On the basis of the biological response, the patients were classified as MR (n=1), PR (n=7), VGPR (n=5) and CR (n=2) after induction and as MR (n=1), PR (n=6), VGPR (n=3) and CR (n=5) before maintenance treatment. Differences in focal lesion detection were observed between MRI and 18F-FDG PET for small lesions (<10 mm). Two false positive focal uptakes were observed (pulmonary infection, sacrum abnormality).The status assessment showed concordant results between the two techniques in only 5/15 (CR, n=2; PR, n=3) and 8/15 (CR, n= 2; PR, n=6) cases at induction and before maintenance respectively. MRI showed residual disease in 7/15 patients before the initiation of maintenance treatment. ConclusionAt diagnosis and during treatment evaluation, both 18-FDG PET and MRI provide information about the extent of the disease, allowing for a more comprehensive assessment of persisting or recurrent myeloma. The morphologic MRI can often be falsely positive due to persistent non-viable lesions. Hence 18-FDG PET might be more suitable than morphologic MRI for determination of the remission status. Disclosures:No relevant conflicts of interest to declare.

Magnetic ordering phenomena of interacting quantum spin Hall models

The two-dimensional Hubbard model defined for topological band structures exhibiting a quantum spin Hall effect poses fundamental challenges in terms of phenomenological characterization and microscopic classification. In the limit of infinite coupling $U$ at half filling, the spin model Hamiltonians resulting from a strong-coupling expansion show various forms of magnetic ordering phenomena depending on the underlying spin-orbit coupling terms. We investigate the infinite-$U$ limit of the Kane-Mele-Hubbard model with $z$-axis intrinsic spin-orbit coupling as well as its generalization to a generically multidirectional spin-orbit term which has been claimed to account for the physical scenario in monolayer ${\text{Na}}_{2}{\text{IrO}}_{3}$. We find that the axial spin symmetry which is kept in the former but broken in the latter has a fundamental impact on the magnetic phase diagram as we vary the spin-orbit coupling strength. While the Kane-Mele spin model shows a continuous evolution from conventional honeycomb N\'eel to $XY$ antiferromagnetism which avoids the frustration imposed by the increased spin-orbit coupling, the multidirectional spin-orbit term induces a commensurate to incommensurate transition at intermediate coupling strength, and yields a complex spiral state with a 24 site unit cell in the limit of infinite spin-orbit coupling. From our findings, we conjecture that in the case of broken axial spin symmetry there is a large propensity for an additional phase at sufficiently large spin-orbit coupling and intermediate $U$.

A quantitative method for correlating observations of decreased apparent diffusion coefficient with elevated cerebral blood perfusion in newborns presenting cerebral ischemic insults

In patients presenting with cerebral ischemic injury, the outcome of injured brain tissue quantified as decreased apparent diffusion coefficient (ADC) may depend on associated alterations in cerebral blood perfusion (CBP). This study proposes a non-biased method to quantify associations between ADC and CBP in newborns with global or focal cerebral ischemia. The study population consisted of nine neonates (age: 0 to 3 days) presenting with clinical and imaging evidence of ischemia (seven with global hypoxic ischemia, and two with focal arterial ischemic stroke) with decreased ADC. Six newborns without diffusion abnormalities on magnetic resonance (MR) imaging served as a comparative cohort (age: 0 days to 4 weeks). All patients underwent MR imaging including diffusion weighted imaging (DWI) to determine ADC and axial arterial spin labeling (ASL) to determine CBP. An algorithm was developed that uses the B0 volume from the DWI raw data as a reference, co-registers the ADC and ASL-CBP data to the B0, generates mask filters, and finally performs a statistical analysis to automatically select regions of interest (ROIs) with ADC or ASL-CBP values that deviate significantly from the rest of the brain. If ROIs are identified in this analysis, the algorithm then evaluates correlation based on ROI location and volume. A significant correlation was found between decreased ADC and elevated ASL-CBP with regions of elevated ASL-CBP typically larger than the corresponding ADC abnormality. The association between decreased diffusivity and increased ASL-CBP suggests that, for this cohort, cerebral ischemia is associated with hyperperfusion.